These artist quality colouring pencils give depth of colour & are easily blendable. To achieve different tonal effects lay down two colours or more on top of one another starting with the lightest colour. Work each pencil in a new direction to ensure a smooth build-up of hues & tints. The coloured strip inside these colouring pencils is more fragile than ordinary graphite pencils & requires extra care when sharpening to protect the pencil strips from breaking. A good metal sharpener should be used but the blades must be changed regularly to prevent damage to the soft pencil strip. Avoid using any sharpener which is too big for your pencil.